flow = cv2.calcOpticalFlowFarneback(prvs,frame_next, None, 0.5, 3, 15, 3, 5, 1.2, 0)

        k = cv2.waitKey(1) & 0xff
        if k == 27:
            break
        elif k == ord('s'):
            cv2.imwrite('opticalfb.png',frame2)
            cv2.imwrite('opticalhsv.png',rgb)
        prvs = frame_next

        for i in range(len(output_image)):
            for j in range(len(output_image[0])):
                if prvs[i][j] != 0:
                    output_image[i][j] = [0, 255, 0]
                    output_image = cv2.arrowedLine(output_image, (j ,i), (j + int(flow[i][j][0]), i + int(flow[i][j][1])), (0, 0, 255), 1)